epifys

Epiphysis (plural epiphyses), sometimes rendered as epifys in some languages, refers to the rounded end part of a long bone. Each long bone has proximal and distal epiphyses. The interior is largely cancellous (spongy) bone containing red bone marrow, while the outer surface is covered by articular cartilage where the bone forms joints with adjacent bones.

Between the epiphysis and the shaft (diaphysis) lies the metaphysis and, in children, the growth plate (epiphyseal or physis). The growth plate is a layer of hyaline cartilage where endochondral ossification adds bone to the metaphysis, yielding longitudinal bone growth. When growth stops after puberty, the growth plate ossifies and forms an epiphyseal line, and the epiphysis fuses with the diaphysis.

Blood supply to the epiphysis is delivered by arteries that enter at the ends of the bone, with additional supply from metaphyseal and epiphyseal vessels. The joint surface is lubricated and nourished by synovial fluid, while the epiphyseal region participates in growth and, in adulthood, in joint articulation and load distribution.

Clinical notes: injuries to the epiphysis, such as epiphyseal fractures, can disrupt bone growth in children. Degenerative changes can affect the articular cartilage of the epiphysis, contributing to conditions like osteoarthritis in later life. In adults, the epiphysis primarily consists of cancellous bone with a thinner cortical shell and houses red marrow in many bones.